There were many liberties taken with individual facts in American Primeval, but I can live with that. The pre-Civil War west was really primitive and violent, and that is what Berg was trying to present.
My bigger issue is the portrayal of Brigham Young. Maybe it is because Kim Coates only knows how to come off like a demented psycho, but I thought the show turned one of the more interesting people of that era in the West into a one-dimensional villain. Brigham Young's behavior during that period was very strategic and ultimately successful. While it is not clear what the U.S. government's intentions were with the Mormons in the late 1850's, I think the Mormons were justified in fearing the American government and Buchanan did not do much to assuage those fears. As leader of the Utah settlers during that war, Young was ultimately successful in protecting his people, and did step down as Governor in return for a full pardon of all the Mormons and preservation of their effective, if not official, governance of Utah Territory. People of the time certainly felt that Young had won the Utah War, calling it "Buchanan's Blunder".
TV and movies will always make the old West more bloody and violent than it really was, but I do not think that was the problem with American Primeval. I think the show's stupid last 30 minutes of the last episode is a much bigger problem.